Question 35

[klee92181]

I thought magnetic induction vector was referring to an induced magnetic field, which would be in the opposite direction of the original magnetic field. Would the mcat be this tricky?

Thanks

[admin]

I'm not sure what you are regarding as tricky. The magnetic induction vector is indeed referring to the magnetic field and they are both described by answer choice D (vector Z).

[deblinak1531]

The diagram is not clear. Using the right hand rule, the induced magnetic field would be clockwise to someone looking down the end of A. Correct?

The problem with the X and Y depictions is that it is not clear which side of the circle corresponds to the front and which corresponds to the back of the wire.

[jvuofm1709]

...the B field vector Z does NOT represent a magnetic induction vector. Magnetic induction is when an electric current is generated by moving a loop through a magnetic field, or rather when it experiences a magnetic flux. Vector Z is merely a property of a moving charge. All moving charges generate a B field vector, there is nothing induced about it. Magnetic induction is generally associated with induced currents in loops which arise from a changing B field. For instance if a loop is in the presence of a B field, and the B field doubles, then that will induce a current in the loop which provides an opposing B field. It is a conservation law, increase a B field to the left, the loop will counter by inducing a B field to the right.

There is no induction in this problem, what deflects the compass is the force tangent to the circular B field of the wire. Since the compass needle is essentially a magnet with north and south poles, it will align itself with the magnetic force vector. The drawing in this example is really really confusing, the diagram should look more like this

http://www.toya.net.pl/~mother/Gimnazjum%20II/Cale%20strony/Magnetic%20Fields%20and%20Forces_pliki/compassneedlesaroundwirerighthandrule.jpg

[jvuofm1709]

here is a picture of a moving bar magnet inducing a magnetic field and emf (and essentially current) in a loop.

http://electron9.phys.utk.edu/phys136d/modules/m8/images/lenz.gif

[jl9523557]

I think this whole passage has many major problems.

1. the wording such as magnetic induction need to be changed to magnetic field vector since it isn't clear if it's referring to the induction or the field.

2. the Y and Z circular vectors are just plain outrageously confusing. they do not indicate which loop is the closer/farther loop looking at them from the test taker's point of view.